I. Field
The present invention relates generally to communication, and more specifically to techniques for processing data for transmit diversity in a multi-antenna communication system.
II. Background
A multi-antenna communication system employs multiple (NT) transmit antennas and one or more (NR) receive antennas for data transmission. The NT transmit antennas may be used to increase system throughput by transmitting independent data streams from these antennas. The NT transmit antennas may also be used to improve reliability by transmitting a single data stream redundantly from these antennas.
A multi-antenna system may also utilize orthogonal frequency division multiplexing (OFDM). OFDM is a modulation technique that effectively partitions the overall system bandwidth into multiple (NF) orthogonal subbands. Each subband is associated with a respective subcarrier that may be modulated with data. The subbands are also commonly referred to as tones, subcarriers, bins, and frequency channels.
For a multi-antenna system, a propagation path exists between each pair of transmit and receive antennas. NT·NR propagation paths are formed between the NT transmit antennas and the NR receive antennas. These propagation paths may experience different channel conditions (e.g., different fading, multipath, and interference effects) and may achieve different signal-to-noise-and-interference ratios (SNRs). The channel responses of the NT·NR propagation paths may thus vary from path to path. For a dispersive communication channel, the channel response for each propagation path also varies across the NF subbands. Since the channel conditions may vary over time, the channel responses for the propagation paths may vary likewise.
Transmit diversity refers to the transmission of data redundantly across space, frequency, time, or a combination of these three dimensions, to improve the reliability of the data transmission. One goal of transmit diversity is to maximize diversity for the data transmission across as many dimensions as possible to achieve robust performance. Another goal is to simplify the processing for transmit diversity at both a transmitter and a receiver. There is therefore a need in the art for techniques to efficiently process data for transmit diversity in a multi-antenna system.